Stroke dependent bypass

Abstract

A shock absorber has a pressure tube with a piston assembly slidably disposed within the pressure tube and attached to a piston rod. The piston assembly divides the pressure tube into an upper working chamber and a lower working chamber. The piston assembly includes a compression and a rebound valve assembly. The piston assembly also includes a housing attached to the piston rod within which is slidably disposed a piston to define a closed chamber. The closed chamber is in communication with one of the working chambers through a passageway extending through the piston rod. The housing and piston provide two stage damping in rebound and compression with a smooth transition between soft and firm damping.

What is claimed is:  
     
       1. A two-stage shock absorber comprising: 
       a pressure tube defining a chamber;  
       a piston member slidably disposed within said pressure tube, said piston member dividing said chamber into an upper working chamber and a lower working chamber;  
       a piston rod extending through one of said working chambers and projecting out of said pressure tube, said piston rod being attached to said piston member;  
       a valve assembly attached to said piston member, said valve assembly providing a first and a second fluid passageway through said piston member;  
       a continuously open third fluid passageway defined through said piston rod, said third fluid passageway extending between said one of said working chambers and a pressure chamber defined by said piston member, said third fluid passage being the only fluid communication path between said one of said working chambers and said pressure chamber said pressure chamber being defined by a housing attached to said piston rod and a piston slidably disposed within said housing;  
       a retaining ring attached to said housing for retaining said piston within said housing; and  
       a first flexible member disposed between said piston and said retaining ring.  
     
     
       2. The two stage shock absorber according to claim  1  wherein said valve assembly includes a compression valve assembly and a rebound valve assembly. 
     
     
       3. The two stage shock absorber according to claim  1  further comprising a second flexible member disposed between said piston and said housing. 
     
     
       4. The two stage shock absorber according to claim  1  wherein said housing is threadingly received on said piston rod. 
     
     
       5. A two stage shock absorber comprising: 
       a pressure tube defining a working chamber;  
       a piston assembly slidably disposed within said pressure tube, said piston assembly dividing said working chamber into an upper working chamber and a lower working chamber;  
       a piston rod extending through one of said working chambers and projecting out of said pressure tube, said piston rod being attached to said piston assembly;  
       a first valve attached to said piston assembly, said first valve providing a first fluid passageway through said piston assembly;  
       a second valve attached to said piston assembly, said second valve providing a second fluid passage through said piston assembly;  
       a housing attached to said piston rod, said housing being adjacent to but separate from said piston assembly;  
       a piston disposed within said housing, said piston and said housing defining a pressure chamber;  
       a third fluid passageway extending between said one of said working chambers and said pressure chamber;  
       a retaining ring attached to said housing for retaining said piston within said housing; and  
       a first flexible member disposed between said piston and said retaining ring.  
     
     
       6. The two stage shock absorber according to claim  5  said housing is threadingly attached to said piston rod. 
     
     
       7. The two stage shock absorber according to claim  5  further comprising a flexible member disposed between said piston and said housing. 
     
     
       8. The two stage shock absorber according to claim  5  further comprising a second flexible member disposed between said piston and said housing. 
     
     
       9. A two-stage shock absorber comprising: 
       a pressure tube defining a working chamber;  
       a piston assembly slidably disposed within said pressure tube, said piston assembly dividing said working chamber into an upper working chamber and a lower working chamber;  
       a piston rod extending through one of said working chambers and projecting out of said pressure tube, said piston assembly being attached to said piston rod;  
       a housing attached to said piston rod, said housing being adjacent to but separate from said piston assembly;  
       a piston disposed within said housing, said piston and said housing defining a pressure chamber;  
       a fluid passageway extending between said one of said working chambers and said pressure chamber;  
       a retaining ring attached to said housing for retaining said piston within said housing; and  
       a first flexible member disposed between said piston and said retaining ring.  
     
     
       10. The two-stage shock absorber according to claim  9 , wherein said piston assembly includes a compression valve assembly and a rebound valve assembly, said compression valve assembly and said rebound valve assembly being separate from said piston in said housing. 
     
     
       11. The two-stage shock absorber according to claim  9 , wherein said piston assembly is slidably disposed on said piston rod and said housing is threadingly attached to said piston rod. 
     
     
       12. The two-stage shock absorber according to claim  9 , wherein said housing secures said piston assembly to said piston rod.